Fig. REF  compares the density fields in our simulation models
Run-Base (left panels) and Run-\(\Delta \) t10kyr (right panels), which differs by the blue
supergiant to Wolf-Rayet phase transition interval. Such transition period is non-existent
in model Run-Base while it is \(\Delta \,t=0.1\, \rm kyr\)  in model Run-\(\Delta \) t10kyr.
Our phase transition timescale is in accordance with both the typical duration of
luminous blue phases \(\sim 10^{4}\, \rm yr\)  and with the timescale of blue-to-red
phase transition [1]}, [2]}.
The Wolf-Rayet nebula in Run-Base is generated by the simultaneous changes of
the wind velocity and density, engendering a peanut-like morphology, which shocked layer
accumulates compressed magnetic field lines, as described in
Section REF .
In Run-\(\Delta \) t10kyr the stellar wind velocity increases first, provoking a more elongated
jet-like nebula, before that the sudden changes in wind density fills it with denser, isotropic
Wolf-Rayet material (see Eq. REF -REF ). In the latter case, Rayleight-Taylor
instabilities form in the equatorial plane, as a consequence of the wind-wind collision
at work therein, see the discussion in [3]}.
This comparison shows that the properties of the time windows during which the wind properties
evolve has a little influences on the overall appearance of Wolf-Rayet nebulae.
Our simplistic setup uses analytic prescriptions that mimic the evolution of
the central massive star, hence, the detailed shape of the nebula might be
slightly different with more realistic, time-dependent stellar wind prescriptions,
e.g. using pre-computed evolutionary tracks [4]}.
